The invention relates to a semiconductor light emitting device and a semiconductor light emitting apparatus, and more particularly, to a semiconductor light emitting device such as a semiconductor laser with a ridge stripe and a semiconductor light emitting apparatus equipped with the same.
In recent years, semiconductor lasers having oscillation wavelengths of 600 to 700 nm have been put to practical use such as in DVD (digital versatile disc). For their further application to writing for DVD-R (recordable) and DVD-RW (rewritable), higher output power is required. One of the device structures of a semiconductor laser that meets such requirements is a “ridge-waveguide type” structure. In a ridge-waveguide type semiconductor laser, lightwave is confined and propagated in a stripe-shaped ridge to control the horizontal transverse mode. Thus it has an advantage that excellent optical output characteristics can be obtained.
In such a high-powered semiconductor laser, the amount of heat generated from its active layer is also increased. For this reason, in order to improve heat dissipation from the laser device, it is desirable to use a so-called “junction down” mounting configuration, in which the p-n junction is mounted in the close vicinity of a submount or other packaging member.
However, in junction down mounting, there is a problem that stress concentrates on the ridge protruding like a stripe, which makes the ridge prone to break. In this respect, a semiconductor laser comprising “dummy ridges” on both sides of the ridge is disclosed (e.g., Japanese Laid-Open Patent Applications 2000-164986 and 2002-223039).
FIG. 30 is a plan view of a semiconductor laser comprising dummy ridges as viewed from its mounting surface.
FIG. 31 is a cross-sectional view along line A-A in FIG. 30.
More specifically, the semiconductor laser 100 shown in these figures has a ridge stripe 112 protruding like a stripe formed on its mounting surface M. Dummy ridges 114 are provided on both sides of the ridge stripe 112. The dummy ridges 114 are continuously formed along the longitudinal direction of the ridge stripe 112.
Current injected via electrodes (not shown) provided on the upper and lower surfaces of the device is narrowed by the ridge stripe 112 and causes light emission at the p-n junction formed on its bottom. The emitted light propagates in the ridge stripe 112 to cause laser oscillation, which is emitted as laser light L from the end face.
When such a laser device is mounted in the junction down configuration, the mounting stress may concentrate on the ridge stripe to cause its breakdown. In this respect, dummy ridges 114 with the same height as the ridge stripe 112 can be provided on both sides of the ridge stripe 112. This can prevent the breakdown of the ridge stripe 112 by dispersing the stress when the mounting surface M is mounted on the packaging member (not shown).